1. Field of the Invention
The invention relates to a method for dividing and combining electromagnetic energy in a coaxial device. In particular, the invention relates to a radial power combiner using flared coaxial lines in combination with broadband tapered slot transitions.
2. Description of the Prior Art
Quine, "Planar Microwave Integrated Circuit Power Combiner," U.S. Pat. No. 4,291,278 (1981), applied to General Electric Company, shows a power splitter and combiner in FIGS. 1, 2, 4, 6 and 8 comprised of a conventional rectangular waveguide 11 used to launch a wave into a taper section 12. An array of waveguide-microstrip fin-lined transitions 13 having tapered slot transitions divides the microwave power equally among two or more microstrip lines. These microstrip lines in turn feed a multistage FET amplifier 15 fabricated in microwave IC form. The array of microstrip-waveguide fin-line transitions 16 therefore combines the power from a plurality of microstrip lines. The fin-line array 13 and 16 as shown in FIG. 1 may be identical to one another with the exception that they face in opposite directions.
Izadian, "Conical Transverse Electromagnetic Divider/Combiner," U.S. Pat. No. 5,256,988 (1993), assigned to Loral Aerospace Corporation, shows in FIGS. 1, 2, 4 and 6 a TEM divider/combiner 10 comprised of an input port 12 feeding a circular waveguide 14. A tapered or conical coaxial device 16 is coupled to circular waveguide 14 and includes a plurality of amplifiers 18 depicted in FIGS. 3 and 4. A second circular tapered waveguide 22 is coupled to an output port 24. As shown in FIG. 2, coaxial device 16 divides a signal using a conical dividing waveguide 42, 32, a first parallel plate waveguide 40, 50 and then a plurality of flared strip lines 54 depicted in FIG. 3. Strip lines 54 couple first parallel plate waveguide 40, 50 to the inputs of the plurality of amplifiers 18. Amplifiers 18 each amplify one of the divided signals and output the results to a second parallel plate waveguide 40, 52. The signals from amplifiers 18 are recombined by this waveguide in the conical combining waveguide. FIG. 6 shows strip line 54 as preferably comprised of a continuous taper for impedance matching between cylindrical coaxial TEM and amplifier 18. Strip lines 54 have similar shapes at each end of the splitter/combiner, however, at each end of the combiner, the strip lines have an opposite orientation.
MacMaster, et al., "Coaxial-to-Cylindrical Array Transition," U.S. Pat. No. 4,272,740 (1981), assigned to Raytheon Company, describes in connection with FIG. 1 a power amplifier having a plurality of amplifying elements 62 disposed in a set of transmission lines 64. Transmission lines 64 are in a unitary structure at cage 66 whereby energy is coupled via a single input terminal 68 and output through a single output terminal 70. The distribution of power among transmission lines 64 is accomplished by power splitter 72. Power from transmission lines 64 is combined by means of power combiner 74. FIGS. 4-21 show a series of stepped and/or tapered transitions in the walls of the transmission lines 64 for the case where the input terminal 68 is coaxial. FIGS. 23-29 show waveguide assemblies 150 coupled via circular waveguides 152 to conical waveguides 154. Conical waveguides 154 are coupled via phase shift assemblies 156 to transition sections 158 which in turn are coupled to cage 66.
Saito, et al., "Device for Distributing and Combining Microwave Electric Power," U.S. Pat. No. 4,588,962 (1986), assigned to Fijitsu Limited, describes in connection with FIG. 13 a splitter in which waves travel in direction A through a rectangular waveguide 31 and are coupled into a plurality of microstrips 133 at their tapered connection regions. Amplifiers are connected to a plurality of microstrip lines 133. As a combiner, the electromagnetic wave travels in direction B and is coupled from the plurality of microstrip lines 33 into rectangular waveguide 131. FIG. 5B shows a flared microstrip line referred to as an antenna. Saito also refers to FIGS. 1 and 2 of Albin, "Integrated Capacitance Structures in Microwave Finline Devices," U.S. Pat. No. 4,789,840 (1988) assigned to Hewlett-Packard Company, and to Swift, et al., "Extra High Frequency (EHF) Circuit Module," U.S. Pat. No. 4,728,904 (1988) assigned to TRW Inc.
Pitzalis, Jr., "Modular Microwave Power Divider-Amplifier-Combiner," U.S. Pat. No. 4,371,845 (1983) assigned to Hughes Aircraft Company, refers to FIG. 1 to a device 10 comprised of a divider 20, plural amplifier modules 15 and combiner 25. A plurality of radially extending microstrip conductors extend to the edge of divider circuit 20 at point 30 and come into contact with conductor 35 of amplifier module 15. Each of amplifier modules 15 is connected to divider 20 and combiner 25 in a similar manner. Coaxial transmission lines 120 carry the wave into and out of device 10. Pitzalis is broadly relevant for showing a radial arrangement of a power splitter and combiner.
What is needed is an RF power combiner which is compact and can be used for high power applications using low power components.